RNA editing by adenosine deamination is believed to occur in most metazoans. It is catalyzed by the ADAR (Adenosine Deaminases that Act on RNA) family of enzymes, which convert adenosine to inosine. During translation inosine is read as guanosine, and therefore this mechanism can change codons in mRNAs. These changes can affect protein structure and function. Any codon change which requires the conversion of adenosine to guanosine is possible. ADARs are composed of a c-terminal catalytic domain that carries out the deamination reaction and two to three double-stranded RNA binding domains (dsRBDs) that bind to the substrate RNA. The dsRBDs are the natural targeting mechanism for ADARs. In natural systems, specific adenosines are selected for editing based on the dsRBDs' ability to recognize secondary and tertiary structure within the surrounding RNA. Often the necessary higher order structures are complex. Our goal is to be able to target ADARs to a selected adenosine. The natural targeting mechanism of ADARs, namely the dsRBDs, would not serve this purpose because they require a specific higher order RNA structure in cis. The probability that such a structure exists around a specific selected adenosine is very low.